What Size Radial Tires to Replace Existing B78-13ST Load Range B Tires on Boat Trailer

Updated 04/28/2014 | Published 04/25/2014

Products Featured in This Question

Loadstar ST175/80D13 Bias Trailer Tire with 13" Galvanized Wheel - 5 on 4-1/2 - Load Range D

(7454)

$143.25

Karrier ST175/80R13 Radial Trailer Tire - Load Range C

(2300)

$96.51

Karrier ST175/80R13 Radial Trailer Tire - Load Range D

(2300)

$104.94

Karrier ST175/80R13 Radial Trailer Tire with 13" Galvanized Wheel - 5 on 4-1/2 - Load Range C

(2433)

$138.12

Karrier ST175/80R13 Radial Trailer Tire with 13" Galvanized Wheel - 5 on 4-1/2 - Load Range D

(2433)

$168.05

Question:

I currently have B78 13ST Load range B on my trailer. FRom what I have read I think I would be better off with a radial tire. Will you tell me the tire size I should purchase. Should I also replace my non-radial spare? Thank you

asked by: Bill C

Expert Reply:

The B78-13 tire you have corresponds to a ST175/80-13 tire size. Radial tires are an excellent choice. They tend to run cooler than bias-ply tires, which will lead to longer tire life.

If you are needing the tire only, we offer that size in a radial load range D (1610 lb capacity @ 65 psi) or a load range C (1360 lbs @ 50 psi). The load D tire is part # AM10210, the load range C tire is part # AM10199.

If your present wheels have a 5 lug on 4-1/2 inch bolt circle, we offer a load range D radial tire on a galvanized wheel, part # AM31994 or a load range C # AM31952.

If your bias-ply spare is still in good shape, you can continue to use it but I wouldn't recommend using it for anything other than emergency use.

Keep in mind, these tires measure 24.1 inches in diameter and 7 inches wide. When upgrading to modern size tires, be sure you have enough room in the wheel well to accommodate this tire size.